Oscillation generator



March 31. 1925. 1,531,633

H. J. VENNES OSCILLATION GENERATOR Filed Dec. 22, 1920 hue/#0)? flaw/a J. V6/7/765.

Patented Mar. 31, 1925.

UNITED STATES PATENT OFFICE.

HAROLD J. VENNES, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

OSCILLATION GENERATOR.

Application filed December 22, 1920. Serial 1T0. 432,393.

To all whom it may concern.

Be it known that I, HARAID J. VENNES, a citizen of the United States, residing atNew- York, in the county of Bronx, State of New 5 York, have invented certain new and useful Improvements in Oscillation Generators, of which the following is a full, clear, concise, and exact description.

This invention relates to a method of and 1 means for generating currents of a plurality of frequencies simultaneously.

The principal object of the invention is to provide an oscillation generator comprising an electric discharge device and an as sociated circuit system adapted to produce currents of more than one requency which are independent of one another. It has been discovered that in order to do this most effectively the oscillation system should not 0 only be given a plurality of natural periods, but the time constants of the ath traversed by each of the currents of di erent fre uenc1es should be made of such values an the grid should be given such an initial ne ative potential, that the sum of the amplitu es of the currents generated in the separate tuned circuits will not be great enough to cause the id to become positive with respect to the filament and will not-cause the tube to distort by operating upon the portion of the input-potenti'al-outputcurrent characteristic which is not substantially linear. When these conditions are met the tendenc of the system will be to oscillate at a plura ity of frequencies at the same time and the currents ofthe different frequencies may be separately varied without affecting the others to any great extent.

By time constant is meant that property of a circuit which determines the interval of time during 'which an alternating E. M; F. must be applied to the circuit to cause a current of definite value to flow through it. In an oscillating circuit if the time constant is small and hence its reciprocal i. e. the ratio of resistance to inductance 5 is large, the

damping of the circuit will be large and the amplitude of the otential ener developed in the circuit w' be small. once by designing the paths traversed by the osclllating current of dilferent frequencies to meet this condition, the potential thereby impressed upon the grid'may be held within the desired limits, as specified above.

Another object is to devise an oscillator for generating currents of a plurality of frequencies whose oscillatory circuits are substantially free from interaction.

According to the present invention these objects and others which will. appear as the nature of the invention is disclosed maybe accomplished by providing an electric discharge device with a feed-back circuit interconnecting its input and output circuits, a pair of tuned circuits having different natural periods, each includin resistances in addition to the ordinary in uctance and capacity. The 0 crating characteristic of such an electric ischarge device, is dependent upon the ratio of grid potential with respect to the filament and the current in the output circuit, ordinarily, i. 0. when no polarizing potential is im ressed upon the grid, has a substantially inear. portion for a short distance on either side of the point representing zero difference of otential between the filament and the gri By limit ing the normal amplitude of the current in each of the oscillatory circuits to a small value and choosing the initial 'd otential at or near the middle of t e straight portion of the characteristic, the sum of the amplitudes of negative. or positive waves will at no time cause the grid potential to move ofi the straight portion.

Two other considerations must be taken into account, however. First, the grid must never be allowed to become positive with respect to the filament, for when this happens t e impedance of the tube is greatly reduced with a resultant change in frequency. This may be effected by impressing an initial negative potential of the proper value uponthe grid, such that, while the tube will operate over a linear portion of its characteristic curve representing the relation between grid potential and output current, the diference of potential between the filament and grid will always be negative. In the second'place when the frequency of any of the oscillatory circuits is changed by changing one of its reactance elements without changing the coupling to the feed-back cir-' cuit, the amplitude of the oscillations generated may be increased. It is necessary I therefore to so choose the amplitude of the currents in the various oscillatory circuits that for all frequency settings their sum will not shift the grid potential off the straight portion of the characteristic curve.

High resistances may be used to determine the time constants of the respective oscillatory circuits, provision being made to adjust said resistances and thereby limit the amplitude of the currents traversing each, or the inductances ma be given high resistance values to pro uce the first condition and a separate adjustable resistancev may be used to effect the regulation of the amplitude of the currents flowing in the respective tuned circuits.

In the drawing, Fig. 1 shows one circuit arrangement for producing currents of two frequencies and Fig. 2 shows a slightly different arrangement for this purpose. 7

Referring to Fig. 1, an electric discharge device 1 is provided with a current source 2 for heating the filament and a source of plate current 3. A source 20 is included in the input circuit of the device to determine the initial potential of its grid or control element. The battery 3 is connected to the plate through a choke coil 4 which prevents short-circuiting the oscillatory current throu h said battery. A condenser 5 is included in the connection to the feed-back and output circuits to impose an infinite impedance to the flow of direct current from plate source 3 to said circuits, whlle providing a path of low impedance for the oscillatory currents.

A feed-back circuit including an inductance 6 is connected across the output circuit of the device. Inductively associated with the coil '6 is an inductance 7 which serves to couple the feed-back circuit with a pair of tuned circuits one of which includes the coil 7, the inductance 8, variable condenser 9 and the adjustable high resistance 10 and the other of which includes coil 7, the adjustable high resistance 11, the variable condenser 12 and the inductance 13. A load circuit may be connected to the terminals 14' and 15. Y

B properly adjusting resistances 10 and 11 the current amplitudes at which the system oscillates may be given any desired value.

The periodicities or natural rates of vibration of the two circuits will be chiefly determined by the value of the inductances and capacities included in each, provided the plate voltage is maintained constant, and may be respectively regulated, within limits, by adjusting either the condensers 9 and 12, inductances 8 and 13, or both.

According to the arrangement shown in Fig. 2, in, which the same elements are designated by the same reference characters provided with subscripts as similar parts in I Fig. 1, a feed-back circuit is connected across the output circuit which includes the inductances 13 6 'and'8 The tuned circuits are coupled to the feed-back circuit of the device by the inductively related coils 6 and 7,. One of the oscillatory circuits includes the inductances 13 6,, the variable condenser 12 and the adjustable high resistance 11,, while the other comprises the inductances 8 6,, adjustable high resistance 10 and a variable condenser 9,.' As in the former showing the resistances 10 and 11 are large and adjustable so that the amplitudes of the currents generated by the system may be kept very small and of the desired value.

An oscillator of this design may be used to generate two independent currents whose frequencies are close together or separated by a large frequency interval depending upon the periodicities of the two oscillatory c1rcuits. Thus, two currents of different audio frequencies may be obtained or one may be of audio and the other of radio frequency.

From the nature of the preceding description it will be evident that the system herein set forth is adapted to produce two independent or non-harmonic currents of different frequencies if the conditions outlined above as to the resistances, time constants and amplitudes of the currents traversing the tuned circuits are observed.

Obviously one frequency determining circuit may be included in the input circuit in the manner shown in Fig. 1 and another in the output circuit in the manner shown in Fig. 2. Again, a plurality of frequency determining circuit may be included in the input circuit as shown in Fi 1 and one or more tuned circuits may be included in the output circuit as shown in Fig. 2, or the frequency determining circuit may be associated with the device in any well-known manner.

It is therefore to be understood that this. invention is not limited to the details herein shown and described but only by the scope of the attached claims.

What is claimed is:

1. An oscillation generator comprising an electric discharge device, an oscillating current circuit connected to said device, a plurality of frequency determining means ofdifl'erent periodiciities, a single means for coupling said oscillating current circuit and said freqeuency determining means and means to maintain the time constants of said frequency determining means small.

2. An oscillation generator comprising a space discharge device, an oscillatin our- 'llO rent path connected thereto, a plurality of reactance elements of said circuits being mutually exclusive except for the reactance of said coupling means.

3. An oscillation generator comprising an electron discharge device, an oscillating current circuit connected to said device, a plurality of tuned circuits of difierent eriodicities, a coupling element includ in said oscillating current circuit, means for' coupling said tuned circuits with said element and means for maintaining the time constants of said tuned circuits small.

4. An oscillation generator com rising an electric discharge device provide with input and output circuits, a.feed-back circuit connecting the input and output circuits of said device, a plurality of tuned circuits of different periodicities each including a high resistance and a single means for coupling said plurality of tuned circuits to said feed-back circuit.

5. An oscillation enerator comprising an electric discharge evice having an anode, a cathode and a control element, a feed-back circuit connecting the cathode and anode and coupled to a circuit connectin the cathode and control element, a plurality of tuned circuits of different periodicities coupled to said feed-back circuit by a single coupling means, means for making said control element initially negative with respect to said cathode and means to limit the amplitudes of the currents traversing said plurality of tuned circuits to such value that said control element does not become appreciably positive.

6. An oscillation generator comprising an electric discharge device having an anode and cathode and a control element, a-feedback circuit connecting the cathode and anode and coupled to a circuit connecting the cathode and control element, a plurality of tuned circuits of different periodicities coupled to said feed-back circuit by a single coupling means, means for making said control element initially negative with respect to said cathode and means to limit the amplitudes of the currents traversing said plurality of tuned circuits to such value that the device operates only over the straight portion of the grid-potential-output-current k characteristic.

7. An oscillation generator comprising an electric discharge device having an anode, a cathode and a control element, a feed-back circuit connecting the cathode and anode and coupled to a circuit connecting the cathode and control element, a plurality of tuned circuits of different periodicities coupled to said feed-back circuit by a single coupling means, means for making said control element initially negative with respect to said cathode, said tuned circuits including means to limit the amplitude of the currents traversing them to such values that said control element does not become appreciably positive.

8. An oscillation generator comprising an electric discharge device having an anode, a cathode and a control element, a feed-back circuit connecting the cathode and anode and coupled to a circuit connecting the cathode and control element, a plurality of tuned circuits of. different periodicities coupled to said feed-back circuit by a single coupling means, means for making said control element initially negative with respect to said cathode, said tuned circuits including means to limit the amplitude of the currents traversing them to such values that said control element does not become appreciably postive or cause the device to operate ofi the straight portion of the grid-potcntial-output-current characteristic.

9. An oscillation generator comprisin an electric discharge device having an anode, a cathode and a control element, a feed-back circuit connecting the cathode and anode and coupled to a circuit connectin the cathode and control element, a plura 1ty of tuned circuits of difierent periodicities coupled to said feed-back circuit by a single cou ling means, means for making said contro element initially negative with respect to'said cathode, said tuned circuits including means to limit the amplitude of the currents traversing them to such values that the device operates only over the straight port-ion of the grid-potential-output-current characteristic.

10. An oscillation generator comprising an electric discharge devicc,,an oscillating current path connected'thereto, a plurality of tuned circuits, a common means for coupling said oscillating current path and said tuned circuits, and means independent of said coupling means for adjusting the periodicities of any of said tuned circuits while maintaining the periodicities of the other tuned circuit substantially constant.

In witness whereof, I hereunto subscribe my name this 16th day of December, A. D.,

HARALD J. VENN ES. 

